In a computer system, a plurality of circuit boards may be connected to establish one or more communication channels. In an Advanced Telecommunications Computer Architecture (ATCA) system, for example, a plurality of circuit boards (also referred to as blades) may be coupled to and interconnected via a common backplane within a shelf or chassis. Electronic components (e.g., chip packages) and connectors may be mounted to the circuit boards. The circuit boards may include conductive paths that electrically connect the electronic components and/or connectors. The conductive paths may include traces that extend along the circuit board and vias that connect the traces to the electronic components and/or connectors mounted on the circuit board. The traces may include signal traces that carry data signals between the electronic components.
Modern communications systems may establish high-speed channels having data rates that approach several gigabits per second (Gb/s) using differential signaling techniques. In such systems, the existing via structures in the circuit boards (e.g., in an 18 layer ATCA backplane) may degrade the high-speed channel performance. This degradation may cause a high-speed channel to fail despite the use of signaling techniques that improve signaling performance, such as de-emphasis in a transmitter buffer and/or equalization in a receiver buffer. The degradation is especially problematic when vias extending through the circuit board (referred to as through-vias) are connected to traces in top signal layers of the circuit board, leaving an unused portion of the via (referred to as a stub) that adversely affects signal integrity. To recover signal quality caused by discontinuity in the vias, an equalization technique may be applied at the circuit level but may be complicated and expensive to implement. One technique for removing the stub includes back drilling the via, which requires an additional manufacturing step and is expensive.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly.